1. Field of the Invention
The present invention relates to a temperature-controlled power supply system and method, and more particularly, to a temperature-controlled power supply system and method capable of maintaining a temperature of a rechargeable battery at a predefined value when the rechargeable battery is under charging.
2. Description of the Prior Art
With the popularization of portable devices, power supply systems with high sustainability and high efficiency are always required. Therefore, high-efficiency rechargeable battery systems are widely utilized in power supply systems. In general, a rechargeable battery is first charged by a power source to store electricity. When a portable device is equipped with the rechargeable battery and turned on, the rechargeable battery starts to supply power to the portable device.
Please refer to FIG. 1, which is a waveform diagram of charging voltage and current of a conventional charging process of a rechargeable battery. In general, the charging process can be classified into three modes: a pre-charge mode M1, a constant current mode M2, and a constant voltage mode M3. As shown in FIG. 1, if the initial voltage of the rechargeable battery is smaller than a pre-charge threshold voltage VLOWV, the charging process falls in the pre-charge mode M1. In the pre-charge mode M1, the rechargeable battery is charged with a lower current. Since the voltage of the rechargeable battery is smaller than the pre-charge threshold voltage VLOWV, the stored electricity of the rechargeable battery is near empty. At this moment, an inrush current or even a larger charging current will reduce the life of the rechargeable battery. After the voltage of the rechargeable battery is greater than the pre-charge threshold voltage VLOWV, the charging process enters the constant current mode M2, i.e. the fast charge mode, and the power source starts to charge the rechargeable battery with a normal current, which is much greater than the current in the pre-charge mode M1. In the constant current mode M2, the charging current remains at a regulation current IREG and the voltage of the rechargeable battery keeps increasing. The regulation current IREG is a current regulated for charging the rechargeable battery according to power efficiency or life sustainability of the rechargeable battery.
After the voltage of the rechargeable battery increases to a regulation voltage VREG, the charging process enters the constant voltage mode M3, and the voltage remains at the regulation voltage VREG and the charging current starts to decrease. After the charging current falls to a termination current ITERM, the electricity stored in the rechargeable battery is near full and the charging process terminates.
As can be seen, in the constant current mode M2, the regulation current IREG is regulated for charging the rechargeable battery according to power efficiency or life sustainability of the rechargeable battery. However, a rechargeable battery may be unavoidably getting old. If the regulation current IREG is most adaptive for a newer rechargeable battery, it may not be still adaptive for an older rechargeable battery. One of the main reasons comes from temperature. For example, temperature may rise when a rechargeable battery is under charging due to the imperfection of power conversion. When the rechargeable battery becomes aging, the charging efficiency may be reduced, which may cause a higher temperature. If the temperature is too high and touches an over-temperature protection level, charging may be stopped, and restarted until the temperature falls to another level. As a result, life of the rechargeable battery may be reduced due to high temperature, and frequent stop and restart of charging may reduce the charging efficiency much more. Thus, there is a need for improvement of the prior art.